The growth of semiconductor III-V compounds by chemical vapor deposition (CVD) using metallo-organic compounds and hydrides as elemental sources has recently developed into a viable process with many potential commercial applications. The metallo-organic chemical vapor deposition (MOCVD) process, based on the pyrolysis of alkyls of group-III elements in an atmosphere of the hydrides of group-V elements, is a common growth technique because it is well adapted to the growth of submicron layers and heterostructures. The metallo-organic molecular beam epitaxy (MOMBE) process is also a popular growth process for III-V alloys.
Open-tube flow systems are used at atmospheric or reduced pressures in producing the III-V alloys. The process requires only one high-temperature zone for the in situ formation and growth of the semiconductor compound directly on a heated substrate.
Low pressure (LP-) MOCVD growth method offers an improved thickness uniformity and compositional homogeneity, reduction of autodoping, reduction of parasitic decomposition in the gas phase, and allows the growth of high-quality material over a large surface area. Growth by MOCVD takes place far from a thermodynamic equilibrium, and growth rates are determined generally by the arrival rate of material at the growing surface rather than by temperature-dependent reactions between the gas and solid phases.
A problem has developed in the preparation of III-V semiconductors by MOCVD or MOMBE methods in that reproducibility of results is generally lacking. The reproducible growth of high quality, perfect single crystal III-Nitrides with low impurity concentration needs a very controlled growth environment. It is known that impurities and specifically oxygen, even very minor levels, can reduce the quality of a MOCVD grown III-Nitride alloy significantly. Therefore, the reduction of the impurity levels in a III-Nitride alloy should improve the reproducibility and quality of the product. More specifically, the elimination of oxygen from the growth environment of the III-Nitride alloy is very important.